How can you test your temp gauge?

[92470]

The stock temp guage in my 71' isn't working. I put in a new sending unit about 6 months ago and it seemed to work, but now nothing. Do any of you know how to "bench test" the gauge, or the sending unit? Is there anyway I can test the wire to make sure it's getting feed all the way through it? I'm up for anything, I just don't want to go dumping parts into it where I don't have to and would just like to know if there are any procedures for isolating the problem.

I have an extra stock temp gauge also that I can use if the one in my dash is bad. Any help is appreciated. Thanks